Capacitors are commonly-used electrical components in semiconductor circuitry, for example in DRAM circuitry. As integrated circuitry density increases, there is a continuing challenge to maintain sufficiently high storage capacitance despite decreasing capacitor area. A typical capacitor is comprised of two conductive electrodes separated by a non-conducting dielectric region. The dielectric region is preferably comprised of one or more materials preferably having a high dielectric constant and low leakage current characteristics. Example materials include silicon compounds, such as SiO2, and Si3N4. Si3N4 is typically preferred due to its higher dielectric constant than SiO2.
Numerous capacitor dielectric materials have been and are being developed in an effort to meet the increasing stringent requirements associated with the production of smaller and smaller capacitor devices used in higher density integrated circuitry. Most of these materials do, however, add increased process complexity or cost over utilization of conventional SiO2 and Si3N4 capacitor dielectric materials.
One dielectric region in use today includes a composite of silicon oxide and silicon nitride layers. Specifically, a first capacitor electrode is formed to have a silicon oxide comprising layer, typically silicon dioxide, of 6 to 10 Angstroms thereover. Such might be formed by deposition, or more typically by ambient or native oxide formation due to oxidation of the first electrode material (for example conductively doped polysilicon) when exposed to clean room ambient atmosphere. Thereafter, a silicon nitride layer is typically deposited by low pressure chemical vapor deposition. This can, however, undesirably produce very small pinholes in the silicon nitride layer, particularly with thin layers of less than 200 Angstroms, with the pinholes becoming particularly problematic in layers of less than or equal to about 75 Angstroms thick. These pinholes can undesirably reduce film density and result in undesired leakage current in operation.
One technique for filling such pinholes is to wet oxidize the substrate, for example at 750° C.-800° C., atmospheric pressure, and feeding 5 slpm H2, 10 slpm O2 for 15-60 minutes. Such forms silicon oxide material which fills the pinholes and forms a silicon oxide layer typically from about 5 Angstroms to about 25 Angstroms thick over the silicon nitride. It is generally desirable, however, to overall minimize the thermal exposure of the wafer/substrate upon which integrated circuitry is being fabricated. Exposure to 750° C.-800° C. for from 15 minutes-60 minutes is significant in this regard.